1. Field of the Invention
The present invention relates to a traffic shaping method and device in communications fields.
2. Description of the Related Art
In recent years, significant progress has been made in implementation of the broadband in IP networks. In accompaniment with this progress, there has been a more and more growing trend to implement high-real-time-property contents such as telephones and broadcasts on the IP networks in addition to Internet traffics such as HTTP and FTP. Properties of the traffics like these and traffic control requirements needed for network environments range over a variety of types. Accordingly, in order to address these various types of requests, availability-having traffic control technologies have become necessary. For example, in the traffics such as HTTP and FTP (which, hereinafter, will be referred to as the Internet traffics), even if some extent of communications discard occurs during communications, this communications discard can be tolerated. This is because integrity of the communications can be ensured by a resending processing based on the TCP/IP. Nevertheless, a control becomes necessary which should be executed over a mechanism (i.e., minimum frame-rate guarantee, or weight-equal frame-rate distribution) for ensuring neutrality of an inter-users frame rate without permitting a bad influence to be exerted on other user's communications by a condition that the utilization frame rate by a particular user is high. On the other hand, in the traffics such as telephones and broadcasts (which, hereinafter, will be referred to as the real-time traffics), this real-time traffics are needed to be equipped with a mechanism for preventing the traffic's bursting (which means that the traffics are sent in large amounts at a time) from occurring while precluding the transfer latency down to the smallest possible degree for implementing smooth communications. If the traffics burst, a reception-packet buffer is needed to be deployed within an appliance (such as, e.g., telephone or set top box) for receiving and reproducing the traffics. Accordingly, there is a danger of causing a problem to occur, such as connectivity due to the appliance. Also, when the IP multicast is used in an image delivery, a buffer for copying a multicast packet and storing the copied packets temporarily in a manner of being expanded is needed to be deployed within a relay device, or a repeater (such as, e.g., Ethernet (: registered trademark) switch), which is a copy point for the multicast packet. At this time, if the traffics burst, a size to be requested for the buffer becomes large. Consequently, there is a danger of resulting in a packet discard due to the buffer shortage, or an increase in the appliance cost.
Also, in an inter-service-points connection in a general enterprise, in many cases, the inter-service-points connection is established via a virtual private network (such as, e.g., Wide-Area Ethernet (: registered trademark)) that has a contract system where charge frame rate differs depending on line speeds. Each user selects a necessary line speed to a service provider to make the contract, thereby ensuring a communications path between the service points. A repeater of the service provider positioned at the entrance of the virtual private network is equipped with a processing function for monitoring the frame rate of each user all the time to supervise whether or not packets whose amount is larger than a contracted frame rate have flown into the repeater, and for discarding excess packets if any. With respect to the traffic which has exceeded the contracted frame rate, the service provider executes its discard regardless of the traffic's degree of importance. In order to avoid the packet discard within the virtual private network, each user deploys the repeater, which is capable of performing a shaping of the traffic in accordance with the contracted frame rate, on a connection line with the virtual private network at each service point. When establishing the connection with respect to a plurality of service points, each user deploys the traffic-shaping-capable repeater on each service-point basis. When addressing the real-time traffics under the circumstances like this, a mechanism becomes necessary which allows the real-time traffics to be transferred with low-discard/low-latency while performing the traffic shaping on each service-point basis simultaneously.
As conventional traffic control technologies, in JP-A-2006-211306 and JP-A-2005-123919, the following traffic control technology is disclosed: Namely, traffics are classified into a high-priority class and a non-priority class. Then, the latency which will occur within the repeater with respect to the traffic classified into the high-priority class is minimized by always transmitting the high-priority traffic with the highest priority. In JP-A-2004-282728, the following shaping method is disclosed: Namely, the peak frame rate and the minimum frame rate are set for each of a plurality of users, then calculating a packet transmission schedule point-in-time for each user. Moreover, scheduling for a transmission timing for the traffic of each user is performed from this transmission schedule point-in-time. In JP-A-2007-013462, the following traffic control technology is disclosed: Namely, a simultaneous traffic scheduling for both the high-priority class and the low-priority class is implemented as follows: The transfer latency of the high-priority class is minimized. Then, when the traffic of the high-priority class is transmitted, a transmission counter of a user is updated by sending the packet length and the user information on the user to a scheduler circuit of the low-priority class. This process allows the implementation of the simultaneous traffic scheduling.
In order to implement the real-time applications such as the high-quality telephones and broadcasts on the IP networks, different traffic control technologies have become necessary, depending on their respective service traffics characteristics and network environments. Hereinafter, the description will be given below concerning network requirements requested, i.e., problems to be solved by the present invention.
Network Requirement (1)
While reducing the discard/latency down to the smallest possible degree with respect to the traffics for which the real-time property is requested, carrying out the traffic shaping for suppressing the burst property of the traffics at the frame rate determined on each flow (i.e., channel) basis. Also, ensuring the neutrality of an inter-users frame rate (i.e., minimum frame-rate guarantee, or weight-equal frame-rate distribution) with respect to the Internet traffics (low priority).
With respect to the above-described problem (i.e., the network requirement (1)), in JP-A-2006-211306 and JP-A-2005-123919, the configuration is that the highest priority is always given to the high-priority traffic. Accordingly, the latency which will occur within the repeater with respect to the high-priority traffic can be minimized. The traffic burst, however, cannot be suppressed on each session (i.e., queue) basis. Consequently, there is a danger of causing a problem that traffic's latency fluctuation (i.e., latency jitter), which occurs by the traffic's having been transmitted via the network, will be propagated as it is. As described earlier, if the mechanism for preventing the burst property of the traffics does not exist on each flow basis, the packet discard due to the buffer shortage occurs in such devices as the reception/reproduction appliance or the repeater which becomes the multicast copy point. Consequently, there is a possibility of resulting in a lowering in the communications quality.
Also, in JP-A-2004-282728, the scheduling for the inter-users packet transmission timings is performed based on the peak frame rate and the minimum frame rate set for each of the plurality of users. In the case of this configuration, however, it is difficult to guarantee sufficient latency quality with respect to the real-time traffics. This is because, in JP-A-2004-282728, the inter-users transmission scheduling processing is performed independently of the type of the traffic with which the communications is being performed. After a user which should transmit the traffic has been determined, a priority control processing or the like is carried out within the user. As a result, the transmission timing for the high-priority traffic is delayed because of the competition of the scheduling processing with the low-priority traffic of another user. As the users which perform the scheduling increase in number, it becomes more and more difficult to neglect the latency due to the inter-users scheduling. Accordingly, it is difficult to offer the sufficient latency quality to the real-time traffics.
Network Requirement (2)
While performing the traffic shaping on each service-point basis, and while reducing the discard/latency down to the smallest possible degree with respect to the traffic for which the real-time property is requested, carrying out the traffic shaping for suppressing the burst property. Also, performing the communications in such a manner that the Internet traffics (low priority) takes advantage of a remaining frame rate which results from subtracting the utilization frame rate by the real-time traffics from the shaping frame rate with respect to each service point.
The difference between the network requirement (2) and the network requirement (1) lies in the point that the discard/latency of the real-time traffic is suppressed while performing the frame-rate limitation of the traffic on each destination-address (i.e., service-point) basis. In the network requirement (1), the traffics are classified on each service basis, then carrying out the shaping/scheduling processing with respect to each classified traffic. In the network requirement (2), on the other hand, the requirement is that the traffic shaping is carried out with respect to the frame rate on each service-point basis including the inter-services frame rate.
With respect to the problem like this (i.e., the network requirement (2)), in JP-A-2004-282728, as exactly described earlier, the problem that the latency is deteriorated for the high-priority traffic is contained therein. Accordingly, it is difficult to reduce the latency with respect to the real-time traffics. Also, in JP-A-2007-013462, the latency of the high-priority class packets is reduced, thereby allowing the implementation of the simultaneous scheduling for both the high-priority class frame rate and the low-priority class frame rate. In JP-A-2007-013462, however, a function for controlling the peak frame rate for the high-priority class packets does not exist. As a result, there is a possibility that the high-priority class traffic will occupy all the line frame rates depending on the traffic input circumstances. In this case, the transmission of the high-priority class traffic at another service point will also be suppressed. Consequently, there is a problem that the traffic shaping on each service-point basis, i.e., the present requirement, will exhibit no effect.